Movable overhead garage doors have been employed for many years. It is recognized as desirable to have a vehicular access door or opening cover that provides adequate protection against environmental elements, such as wind and rain, and that also prevents forced entry into the garage. Over the years, several types of doors have been developed to cover or control the openings to buildings where the openings are large enough to allow a vehicle to pass through.
The most common of these doors in the United States are sectional garage doors that have a series of panels or sections attached to one another by hinges. The panels are substantially vertically aligned when the door is closed and substantially horizontal when the door is open. A plurality of track rollers are attached at the sides of the sectional door and are rollingly journaled in tracks mounted inside the door opening. The tracks are disposed vertically at the sides of the door and curve near the top of the door opening thereby making a transition to be horizontally disposed along the garage ceiling. Thus, as the door is moved relative to the track, it is first moved upward and then inward as the panels or sections hinge at the transitional track curve. Accordingly the door is stored in the overhead area of the garage when in the open position. Further, the door may be counterbalanced by way of torsion and/or extension springs to assist in opening the door. This is accomplished by causing the springs to be tensioned such that the counterbalance tension equals the weight of the door when the door is closed.
In practice, several disadvantages have become apparent in conjunction with the use of such doors. The first of these disadvantages relates to the shipping and installation of the doors. Typically these door systems are shipped disassembled and, accordingly, in most situations must be assembled during installation. Initially, the track sections must be mounted in the door opening and in the ceiling area. The overhead track sections are, depending on the building structure, often positioned some distance from the ceiling, and the furthermost inward portion of the track must be supported from the ceiling by what is known as hanger brackets. Because building structures vary greatly from application to application, the hanger brackets typically must be cut to length to fit the application. After the track is installed, the individual panels are fitted in the door opening and attached together using the hinges. Then the counterbalance springs must be attached and adjustments made in track position, spring tension, and roller position, so as to ensure proper operation. Thus, the installation of such doors can be quite labor intensive.
Other disadvantages of the aforementioned doors relate to the operation and storage thereof. Sectional garage doors are often quite noisy due to the combination of rollers striking the guide track and hinges squeaking when opening or closing the door. While lubrication is helpful in reducing noise, it does not eliminate it. Additionally, sectional doors require a storage area in the overhead position of the building substantially equivalent to the size of the opening itself. Such space is sometimes unavailable and thus precludes the use of doors of this type.
A second type of garage door, most common in Europe, is a one-piece door comprising a single section that pivots around a point about midway up the vertical distance of the opening and somewhat inside the building. This type of door is also rollingly journaled in tracks mounted at the sides and top of the door and is also stored in the overhead area of the building. Accordingly, the one-piece door suffers from many of the same drawbacks as sectional doors.
Track systems have been developed for one-piece doors so as to reduce headroom requirements. This is accomplished by locating the pivot point of the door such that the top of the door section will move basically parallel with the ceiling. To accomplish this, however, the door must move significantly into the room or significantly outside the room when moving from closed to open and vice versa. Thus, the building must be deep enough to allow the intrusion of the door without striking a stored vehicle if the door moves inside the building, or clearance must be maintained outside the building if the door moves outside. As with sectional doors, reinforcing members added to the back of the door tend to cause the door to become more intrusive into the building both in the closed and open positions.
Another type of door commonly employed is essentially a modification of the one-piece door. The bi-folding door is made of two sections that fold in the center when the door is opened. The bi-folding door also suffers from many of the disadvantages of the aforementioned doors but requires a storage area only about half the depth of the one-piece door and about twice the thickness.
Yet another type of door is the folding door, which consists of a plurality of panels or sections that fold together when the door is in the open or stored position. While these types of doors significantly reduce the depth into which the door extends into the building when open, the thickness of the storage area is significantly increased, requiring a thickness approximately equal to the height of the panels or sections. Typically, such doors are shipped unassembled and are assembled during installation. Again, these types of doors tend to be quite noisy, having rollers and folding sections which pivotally contact one another. Further, due to the sections or panels folding together when stored, folding doors are limited in the amount of reinforcement that can be added without affecting the ability of the doors to fold together in the open or stored position. Also, due to the method of folding, the doors have a tendency to gather where hinged areas are not supported by track and lose their sealing abilities when experiencing wind velocity pressures.
Yet another type of opening cover for a garage door opening is a rolling door that consists of a plurality of slats or sections, which are relatively narrow in height and are rolled up on a storage drum when the door is open and in the stored position. The diameter of the storage drum is directly proportional to the height of the slat. Accordingly, the narrower the slat, the smaller the radius around which it can be stored, thus allowing the use of a smaller storage drum. The slats or sections are designed to pivot at the slat-to-slat interface so that storage on a round drum surface is possible. The area required to store a rolling door in the open position is a function of the height and thickness of the slats or sections. As the slats or sections increase in height, the diameter of the storage drum must become larger to prevent damage to the slats or sections of the door when the door is stored. Further, the thicker the slats or sections become, the greater the outside diameter of the stored door, thus increasing the area required to store the door when opened. Rolling doors can be shipped already assembled and wrapped around the storage drum. Installation requires setting the track system and drum support brackets, and then placing the storage drum with the door into the support brackets. Rolling doors can have rollers, but more often the slats are guided directly in the track. Accordingly, there is a considerable amount of noise generated from slat-to-slat contact and from slat-to-track contact during opening or closing of the door.
Some rolling doors, as described above, are limited in the amount of reinforcing that can be added without affecting the size of the storage area for the door in the open or stored position. It is common to use locking devices known as "windlocks," which are located on the portion of the slat or section that rides in the track system so as to transfer to the track system wind velocity pressure, thereby improving performance of the door during periods of high wind. However, these "windlocks" sometimes cause sections or slats to become jammed, thereby preventing the door from operating properly. On motor-driven rolling doors, the motor turns the storage drum, and the sections or slats not driven rely on gravity to pull the sections or slats into place. If an obstruction is encountered, the sections or slats have no place to go and become jammed against one another inside the roller barrel, which tends to severely damage the slats and/or track system. Such damage to the slats or sections can prevent the door from opening or closing properly.
In motor-operated rolling doors, the motor is commonly located inside the storage drum. Thus, any service to the motor requires disassembling the door and storage drum, resulting in an increase of labor and/or cost. Further, sealing the top of the door against the header of the opening requires the storage drum to be located significantly above the opening so that the door can be routed close to the header as the door uncoils from the drum and the diameter of the stored door decreases and the distance between the outside surface of the stored door on the storage drum and the header increases.
In recent years, there has been a greater awareness of the considerable damage caused to buildings and structures due to severe weather conditions. As such, garage door systems have come under scrutiny as a possible component of buildings that, if strengthened, could prevent further damage to the buildings. As a result of pressure from insurance companies and the public in general, building officials have taken steps in some geographic areas to increase building code requirements for resistance to wind and debris impact. Accordingly, designers of building components, such as garage doors, have attempted to improve wind and impact resistance by increasing door thickness and/or adding reinforcing trusses or beams to the backs of doors. However, such methods have seriously affected the weight of the door, thereby requiring heavier, stronger door components, such as springs and tracks, as well as reinforced structural support in the building itself. The need for such reinforcement has, therefore, increased labor and cost in installing such doors.
In many installations, especially in Europe, door openings are not standard. Thus, installers must either adapt the opening to fit the door or adapt the door to fit the opening. Of course, if the door is wider than the opening, the door must be cut to fit. If the door is a sectional, one-piece, or folding door, the end stiles may be removed and the panel(s) shortened by half the amount on each side to maintain the symmetry of the door. Changing the height of a sectional, one-piece, or folding door is difficult, and typically installers simply allow the door to extend above the opening on the inside of the structure rather than cutting the door down. Of the various door types discussed above, the rolling door can be most easily cut down in width and can have removable slats to adjust the height.